Theory:

Law of parallelogram of forces:

When two forces react simultaneously at a point are represented in magnitude and direction by two adjacent sides of a parallelogram, then their resistant is represented both in magnitude and direction by the diagonal of the parallelogram passing through the point of intersecting of two forces.

Procedure:

Clamp the board in vertical position by a plumb line and pin the sheet of paper on it with drawing pins.

The short string in middle of first string to make a knot at 0. Tie the unknown weight at other end. Arrange them on pulleys.

Adjust the weight so that know is in middle of the paper.

When the know comes to rest, mark it on paper.

Repeat the procedure a couple of times.

Remove hangers along with weights and carefully weigh each hanger and slotted weight.

Keep board flat and join the three points to meet at 0. Select a suitable scale and cut lengths OA and OB.

Repeat above set of observation for three more sets of weight.

Sources of Error:-

Pulleys may have friction.

Weights may not be accurate.

Points may not be marked correctly.

Weight measured by spring balance may not be much accurate.

Observations:-

Forces

Slides

Resultant for R (g wt)

Unknown weight S(g wt)

Weight of Spring (g wt)balance

Error (g wt)

P (g wt)

Q (g wt)

OA (cm)

OB (cm)

200

4

200

4

5.9

295

290

5

Diagram:-

Result

– The unknown weight of given body is found to be 290 g.

Viva Questions:-

______ represents the resultant of the vector addition in parallelogram law of vector.

Diagonal of the parallelogram

Friction in the pulleys is one of the sources of error in the experiment using Gravesand’s apparatus. True or False.

False

Mass is a vector quantity. True or False.

False

Define Vector

Physical quantities, having both magnitude and direction are called vector quantities.

ii) If DD be the mean diameter and l be the length of the wire, then volume of wire
V = π(D/2)2l = (πD2l)/4

Procedure:

Measurement of the Diameter

First of all calculate the pitch and the least count of the given screw gauge.

Find the zero error with its proper sign. Even after when the zero error is nil, this fact too should be recorded.

Now insert the wire between the screw and the steed of the screw gauge. Move the screw forward by rotating the ratchet till the wire is gently gripped between the screw and the steed. Stop rotating the ratchet the moment you hear click sound. In case the ratchet is not properly functioning, rotate the circular cap with the help of your fingers, till your fingers start slipping. Do not press or rotate the cap too hard. Record the readings on the main scale and the circular scale as explained above and add the two readings. This gives the observed diameters.

Take the mean of these observed diameters.

Apply the zero correction with its proper sign to the mean observed diameter and find the correct diameter.

Make a record of your observations as detailed below.

Measure the length of wire by stretching it along a metre scale.

Sources of Error:-

Backlash error: It occurs due to wear and tear of the screw threads, it is observed that reversing the direction of rotation of the thimble, the tip of the screw does not start moving in the opposite direction immediately, but remains stationary for a part of rotation. This is called back lash error. It occurs if we move the screw in one direction and then in opposite directions repeatedly.

Zero error: If on bringing the flat end of the screw in contact with the stud, the zero mark of the circular scale coincides with the zero mark on base line of the main scale, the instrument is said to be free from zero error. Otherwise an error is said to be there.

Observations

:-

Main/Linear Scale Reading (M.S.R.)

Circular Scale Reading (C.S.R.)

Total observed reading (D) = M.S.R. + (nxLC) (mm)

No of circular scale division in line with main scale (n)

n x L.C.(mm)

8

43

0.043

8.043

8

47

0.047

8.047

8

46

0.046

8.046

Length of the wire = 27cm

Calculations

:-

Mean Observed Reading = (8.043+8.047+8.046)/3 = 8.0453 mm

Volume of wire = (πD2l)/4 = π(8.0453/1000)2(0.27)/4 = 0.00001372757m3

Diagram

:-

Result – The diameter of the given wire is measured by using a screw gauge is 8.0453 mm. The volume of the wire is 0.00001372757m3.

Viva Questions:-

What is least count?

The distance through which the screw advances when it is rotated through one division of the head scale.

What is the least count of the screw gauge if the head scale of a screw gauge contains 100 divisions and its pitch is 1 mm?

0.01mm

Screw gauge is less reliable than Vernier calliper in measuring the dimensions of an object. True or False.

When the p section of the diode is connected to positive terminal and of a battery and n section is connected to negative terminal of the battery then junction is said to be forward bias with an increase in bias voltage the forward current increases slowly in the beginning and then rapidly. At about 0.7 V for SI diode (0.1 V for Ge), the current increase suddenly. The value of forward bias voltage, at which the forward current increases rapidly, is called cut in voltage or threshold voltage.

Procedure

Make circuit as shown in the circuit diagram.

Make all the connection neat and tight.

Note at least count and zero error of voltmeter (V) and milliammeter (mA)

The resistance (r) of a resistance wire or coil is given by r=(100-l)/L *R where R is the resistance from resistance box in the left gap and L is the length of meter bridge wire from O end upto balance point.

When r1 and r2 are connected in parallel , then their combined resistance

Rp = r1r2 /r1+r2

Procedure

Mark the two resistance wires as r1 and r2

Connect the two coils r1 and r2 in parallel as shown in fig. in the right gap of meter bridge and find the resistance of this combination . Take at least three set of observation

Record your observation .

Result

Within limit of experimental error , experimental and theoretical values of Rp are same .